Heat exchanger, reservoir, fan and pump assembly



July 27, 1965 A. R. ERBE ETAL 3,

HEAT EXCHANGER, RESERVOIR, FAN AND PUMP ASSEMBLY Filed Dec. 14, 1959 s Sheets-Sheet 2 United States Patent 3,196,939 HEAT EXCHANGER, RESERVOIR, FAN AND PUMP ASSEMBLY Alfred Roscoe Erbe, Oak Park, and Douglas E. Mueller,

Elgin, lll., assignors to The Haliicrafters (10., a corporation of Delaware Filed Dec. 14, 195R, Ser. No. 859,214 2 Claims. (Cl. 165-107) This invention relates to a heat exchanger which is particularly designed for air-borne use as in airplane or missiles.

Present day aircraft and particularly large commercial and most military planes and missiles incorporate equipment, primarily electrical or electronic in nature, which generates a substantial amount of heat. To permit compact assembly of such equipment forced cooling is required to maintain the temperature of the equipment within reasonable limits. A heat exchanger for air-borne use must be light, compact and efficient, providing maximum cooling with minimum weight, space and power requirements. In one specific system a heat transfer medium is circulated through the equipment to be cooled, where it picks up heat, and through a heat exchanger where the fluid is cooled, as by flowing air across heat transfer surfaces.

A principal feature of this invention is a heat exchanger particularly designed to fulfill the requirements for air-borne use.

A more particular feature of the invention is the provision in a heat exchanger of a multiple section heat transfer structure having an inlet and an outlet, means for moving air in heat transfer relation with the structure, the air passing sequentially over the sections from a section adjacent the outlet to a section adjacent the inlet, and means for passing a transfer medium sequentially through the sections of the structure from the inlet to the outlet. Thus the heat transfer fluid receives its final cooling from the incoming cooling air, resulting in maximum efficiency for the system.

Another feature is the provision in a heat exchanger of means for passing a heat exchange medium through a heat transfer structure, a fan for moving air in heat transfer relation with the structure, a drive for the fan and means forming a part of the drive for maintaining a torque to the fan relatively constant with varying load on the fan. This is particularly important in an airborne heat exchanger operated from a constant speed motor as the load on the fan changes at different altitudes with variations in air density. The loosely coupled fluid drive between the motor and fan provides for the delivery to the fan of relatively constant torque and the efficiency of the system is maintained at high latitudes.

A further feature of the invention is the provision of a heat transfer structure comprising a section of tubing having a flattened cross section such that the heat transfer fluid flows through it in a relatively thin sheet and is at substantially the same temperature across the thickness of the sheet with uniform, rapid and efficient cooling.

Still another feaure is the provision in a heat exchanger of a frame having a wall portion defining a reservoir for a heat transfer medium, the wall also defining a motor mounting recess, an inlet for a heat transfer medium connected with said reservoir, a motor mounted in the recess, a heat transfer structure mounted on the frame, a pump driven by the motor and having an inlet condhhfi fi Patented July 27, 1965 nected with the reservoir and an outlet connected with the heat transfer structure, and a fan driven by the motor for moving air over the structure.

Further features and advantages of the invention will readily be apparent from the following specification and from the drawings in which:

' ture with a portion in section as indicated along line 6-6 of FIGURE 7;

FIGURE 7 is a section taken generally along line 77 of FIGURE 6;

FIGURE 8 is a section taken generally along line 3-8 of FIGURE 6;

FIGURE 9 is an enlarged fragmentary section through the heat transfer tubing; and

FIGURE 10 is a section through the fan drive coupling.

Present day aircraft and particularly military aircraft utilize a great deal of electronic equipment for communications, navigation, fire control and the like. Many of the components of this equipment generate heat, as electronic tubes, resistors, etc., and yet must be kept below certain temperatures for proper operation. In order to conserve space, which is at a premium in aircraft, the equipment must be assembled in a compact manner and to maintain-the proper temperature levels forced cooling is required. The cooling equipment must itself be compact, light in weight and must operate efficiently over a wide range of altitudes.

Turning now to the drawings, FKGURE 1 illustrates in schematic form an embodiment of the invention. The equipment to be cooled 15, which may be a rack of electronic equipment, has provision therein (not shown) for the circulation of a heat transfer medium in a manner to pick up heat generated by components of the equipment. The heat transfer medium flows to the equipment 15 through a conduit 16, at a relatively low temperature and the heated transfer medium flows from the equipment 15 through conduit 17. The heat exchanger which forms the present invention is embodied in the elements illustrated to the right of broken line 18. The transfer medium from equipment 15 flows through conduit 17 to a reservoir 19 from which it is forced by pump 20 into conduit 21. The heat exchange structure 22 includes a plurality of sections (here 5) designated 22a, 22b, 22c, 22d and 22e. Conduit 21 is connected with an inlet 23 provided in section 2211 and the heat transfer fluid preferably flows sequentially through the sections from left to right as shown in FIGURE 1. An outlet 24 provided in section 22a is connected with conduit 25 through which the cooled heat transfer fluid is returned to conduit 16. A fan 26 moves air across and in heat transfer relation with the heat exchange structure 22, the air flowing from right to left as indicated in the drawing. Fan as is driven by motor 27 which also drives pump Zti. Bypass conduit 28 is connected between conduits 21 and 2S and flow of heat exchange medium through it is controlled by a thermostatic valve 29. When the temperature of the heat exchange medium is such that no cooling is necessary, valve 29 permits the medium to flow through bypass conduit.

The hot heat transfer fluid preferably enters the heat exchange structure in section 22a closest to fan 26 and exits through outlet 24 from section 22e farthest from the fan. The heat exchange medium flowing through the sections of the heat transfer structure is gradually cooled by the air flow while the cooling air which is drawn in by the fan passes first over the final section 22: resulting in maximum cooling of the heat exchange medium before it is returned to equipment 15.

In previous systems of this type variations in density of the air in the wide range of altitudes in which the equipment must operate has resulted in poor overall efficiency of the system. In accordance with the present invention a fluid coupling 32 is interposed in the drive between motor 27 and fan 26, the slip of the coupling varying in accordance with the load on the fan and maintaining the torque to the fan relatively constant regardless of the density of the air in which the system operates. It has been found that this fluid coupling delivers relatively constant cooling with variations in air density and requiring almost constant power from the motor. For example, the approximate change in density of the air from sea level to 70,000 feet is by a factor of 16. in order to move the same volume of air at sea level as at 70,000 feet would require 16 times as much input power to motor 27. However, the cooling effect of a given volume of air varies with density and the volume of air required for constant cooling of the heat exchange medium is much less at sea level than at higher altitudes. The illustrated system provides substantially constant cooling with constant input power requirements.

Turning now to FIGURES 25, the structure of a physical embodiment of the heat exchanger apparatus will be described. The unit is designed for panel mounting in a rack along with other elements of electronic equipment and includes a cast frame 35, as of aluminum. Formed as an integral part of frame 35 are walls 36 defining reservoir 19 for the heat exchange medium. A recess 37 is formed in the center of reservoir 19 and receives pump and fan drive motor 27. Pump 20 is mounted on one end of the motor housing and has an inlet 38 connected with reservoir 19 and outlet 39. The armature shaft 40 of motor 27 is connected through fluid coupling 32 with fan 26 which is located in a reduced section 41 of frame 35 providing a shroud or venturi about the fan blades, enhancing the operation of the fan. The sections of heat exchange structure 22 are carried between extensions 35a of the frame and will be described in more detail below. The heat transfer medium is delivered to the heat exchanger through conduit 17 connected with an inlet fitting 42 from which it passes directly into reservoir 19. Pump 2% draws the fluid from the reservoir through pump inlet 38 and discharges it through outlet 39 into conduit 2f. connected with the inlet 23 of heat exchange structure section 22a. The heat exchange medium passes sequentially through the sections of the heat exchange structure where it is cooled by the air drawn over the structure by fan 26. From section 222 the fluid passes through outlet 24 into conduit 25 and through control valve 29 and outlet fitting 44 to conduit 16 through which it returns to the equipment being cooled.

Turning now to FIGURES 6-9 the heat transfer structure itself will be described. Each of the heat transfer sections 22a22e includes a plurality of heat exchange tubes 46 with the ends of the tubes of each section mounted in headers or manifolds as 22a22a". The heat transfer fluid which flows through inlet 23 to header 22a passes generally uniformly through each of the tubes 46 in section 22a, to header 22a from which it flows through ports 47, there being one at the top and the bottom of the header, to header 22b in section 225. The heat transfer fluid flows back through the tubes 46 of section 22b in a direction opposite its flow in section 22a, and into header 22b. The part arrangement is repeated through the remainder of the sections of the heat transfer structure with the heat transfer fluid reversing flow direction in adjacent sections. Conduit is connected with the outlet 24 in header 22a of section 222.

The flattened cross section configuration of tubes 46 is extremely important in establishing the efficiency of the overall system. Flattened tubing provides a substantially greater hcat radiating surface area for a given flow capacity than with round tubing. Furthermore, the flow of heat transfer fluid through the tubing is in a thin sheet or laminar in nature and temperature gradient in the fluid itself is minimized. This results in more rapid and uniform cooling of the fluid. In one form of the invention tubing 46 is one inch wide, one-eighth of an inch thick and has a one-thirty-second inch wall. The flow passageway 46a defined by the tubing has a minor dimension of the order of one-sixteenth of an inch.

Many types of heat transfer fluids are suitable in a heat exchanger of this type, including certain hydraulic fluids as 0845 sold by Monsanto Chemical Co. and DC200 sold by Dow Chemical Co.; and a water and ethylene glycol mixture, or the like.

In FIGURE 10 the construction of loosely coupled fluid coupling 32 is shown. Motor shaft 46 has mounted thereon the impeller 50 of the coupling with an extension 52 of the shaft received in an outboard bearing (not shown). The housing 51 of the coupling is rotatably mounted on shafts and S2 and has the fan 26 secured thereto. A suitable hydraulic fluid fills the interior of housing 51 and as impeller is rotated, housing 51 is rotated with it. The slip or difference in rotational speeds of the impeller and housing increases with the load on fan 26 so that the fan runs at a lower speed at low altitudes than at high altitudes. As pointed out above, the fluid coupling in the system provides an operation in which both the cooling operation and the power consumption of motor 27 are maintained substantially constant over a great range of altitudes.

While we have shown and described certain embodiments of our invention, it is to be understod that it is capable of many modifications. Changes therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

We claim:

1. A heat exchanger of the character described, comprising: an elongated frame of rectangular cross-section, said frame having an axis; walls defining a reservoir extending transversely of said frame and having an axial opening therethrough; a multiple section heat transfer structure mounted on said frame, each section of said structure extending transversely across said frame and having a plurality of tubular elements with an inlet manifold at one side and an outlet manifold at the other; means interconnecting said outlet and inlet manifolds serially interconnecting the tubular elements of said sections for flow of heat transfer medium therethrough, each section extending across said frame and the successive sections being aligned along the axis of the frame; a quantity of heat transfer medium for flow from said reservoir through the tubular elements of said structure; a motor mounted in the opening of said reservoir; :1 pump driven by said motor and connected with said reservoir and heat transfer structure to circulate the heat transfer medium therethrough; a fan driven by said motor and causing an axial flow of air across the successive sections of said heat transfer structure in a direction opposite to the general flow of heat transfer medium therethrough.

2. The heat exchanger of claim 1 wherein each section of said heat transfer structure includes a plurality of parallel, straight flat tubular elements joined by manifolds at each end, the surfaces of each tubular element being inclined with respect to the axis of said frame, the surfaces in each section being parallel and the surfaces in alternate sections forming generally equal and opposite angles with respect to said axis.

References Cited by the Examiner UNITED STATES PATENTS 1,803,505 5/31 Macleod 165-107 1,855,032 4/32 Sinclair 318-433 X 1,905,811 4/33 Culver 165-47 2,006,649 7/35 Modine 165-146 2,216,747 10/40 Klirnek 29-156.8 2,237,516 4/41 Young 165-82 Zeidler 29-1568 Lehmann 165150 Elfving et al. 62-505 Nutt 123-4112 Oldberg 230-471 X Hardy.

FOREIGN PATENTS Great Britain.

CHARLES SUKALO, Primary Examiner.

ERMAN BERMAN, HERBERT L. MARTIN, PERCY L. PATRICK, Examiners. 

1. A HEAT EXCHANGER OF THE CHARACTER DESCRIBED, COMPRISING: AN ELONGATED FRAME OF RECTANGULAR CROSS-SECTION, SAID FRAME HAVING AN AXIS; WALLS DEFINING A RESERVOIR EXTENDING TRANSVERSELY OF SAID FRAME AND HAVING AN AXIAL OPENING THERETHROUGH; A MULTIPLE SECTION HEAT TRANSFER STRUCTURE MOUNTED ON SAID FRAME, EACH SECTION OF SAID STRUCTURE EXTENDING TRANSVERSELY ACROSS SAID FRAME AND HAVING A PLURALITY OF TUBULAR ELEMENTS WITH AN INLET MANIFOLD AT ONE SIDE AND AN OUTLET MANIFOLD AT THE OTHER; MEANS INTERCONNECTING SAID OUTLET AND INLET MANIFOLDS SERIALLY INTERCONNECTING THE TUBULAR ELEMENTS OF SAID SECTIONS FOR FLOW OF HEAT TRANSFER MEDIUM THERETHROUGH, EACH SECTION EXTENDING ACROSS SAID FRAME AND THE SUCCESSIVE SECTIONS BEING ALIGNED ALONG THE AXIS OF THE FRAME; A QUANTITY OF HEAT TRANSFER MEDIUM FOR FLOW FROM SAID RESERVOIR THROUGH THE TUBULAR ELEMENTS OF SAID STRUCTURE; A MOTOR MOUNTED IN THE OPENING OF SAID RESERVOIR; A PUMP DRIVEN BY SAID MOTOR AND CONNECTED WITH SAID RESERVOIR AND HEAT TRANSFER STRUCTURE TO CIRCULATE THE HEAT TRANSFER MEDIUM THERETHROUGH; A FAN DRIVEN BY SAID MOTOR AND CAUSING AN AXIAL FLOW OF AIR ACROSS THE SUCCESSIVE SECTIONS OF SAID HEAT TRANSFER STRUCTURE IN A DIRECTION OPPOSITE TO THE GENERAL FLOW OF HEAT TRANSFER MEDIUM THERETHROUGH. 